1. Field of the Invention
The instant disclosure relates to structural arrangement of semiconductor device and fabrication method thereof, and pertains particularly to a semiconductor device having trench gate and fabrication method thereof.
2. Description of Related Art
Channel length of a semiconductor device having trench gate is generally determined by the etch depth of the trench for a gate and the ion implantation depth of the source/drain area. The trench for a gate is conventionally formed by one-step etching of the semiconductor substrate. This may result in a large trench depth difference between the different sections (e.g. the center section and the edge section) of a semiconductor wafer, thus, the channel lengths of the semiconductor wafer are not uniform. That is to say, process uniformity is not easily controlled and there is a problem of channel length variation and/or gate length variation in the prior arts.